Field of the Invention
The present invention relates to a five phase power distribution system and, more particularly to a five phase power distribution system to provide increased energy efficient and harmonic reduction.
Description of the Prior Art
Three phase electrical power systems are commonly used in generation, transmission, and distribution of electric power. A three-phase system is a generator-load pair in which the generator produces three sinusoidal voltages of equal amplitude and frequency but differing in phase by 120 degrees. It is a type of polyphase system which is the most common used by electric power distribution grids worldwide. The three-phase system was introduced and patented by Nikola Tesla in the years from 1887 to 1888.
In a three-phase system, three circuit conductors carry three alternating currents, of the same frequency, which reach their instantaneous peak values at different times.
Traditional electrical system design had very little to do with harmonics because the loads typically designed were linear in nature. Because a substantial portion of the today loads are nonlinear in nature, producing harmonics, in today electrical system design they should be taken into consideration.
Harmonic currents come from electronic equipment such as: adjustable-speed motor drives, fluorescent lighting, personal computers and home electronics. Harmonic currents result in additional heat losses, reduce efficiency and operation of the devices, and reduce power factor. Overheating of electrical cables and wiring has been most prominent in commercial buildings with a high usage of electronic-type equipment. Increased current that contains more harmonics leads to higher distribution network and wiring losses per watt of connected load.
Predominant harmonics are: 3rd, 5th and 7th. These harmonic are known to cause problems for users as well as for maintenance and operation. No cost effective and ultimate method have been proposed that can universally deal with 3rd, 5th and 7th harmonics during the design and specification stage of three phase electrical distribution systems.
Over the years, several approaches evolved and became widely used to improve operations of three phase systems, address the harmonics issues and mitigation techniques:
1. Multiphase, especially a 6-pulse and 12-pulse system is producing less ripple with a higher frequency of ripple in an ac/dc rectifier system. The reason of choice for a 6 phase, 12 phase, or 24 phase system is that these numbers are multiples of three and designing this type of system is simple and straightforward. However, increasing the number of phases certainly enhances the complexity of the system. None of these designs are available for an odd number of phases.
2. The PWM technique and special transformer connections are used to convert three phase systems to five-phase systems, and in the late 1970s were used for adjustable speed drive applications. Since then, a considerable research effort has been conducted to develop commercially feasible multiphase drive systems. The reliability of such systems is diminished due to the use of power electronics. The quality of the converted voltages can be questionable and the amount of transferred power can be limited.
3. Phase-shifting transformers of different configurations, used for decades in industrial and computer facilities, typically treat harmonics produced by loads that are balanced and connected phase to phase e.g. 5th, 7th, 11th, 13th harmonics. By integrating phase shifting of multiple outputs, substantial reduction of 3rd, 5th and 7th harmonics can be achieved. The systems works in case of balanced load. Since the load is mostly unbalanced the full benefits of such are tremendously reduced. It requires several transformers to create such system.
4. Three phase zero sequence filters, zig-zag reactors, etc., have been used in commercial and institutional settings to reduce triplen harmonics, 3, 9, 15, . . . , and associated problems, high neutral current, voltage distortion, etc.
5. For harmonic mitigations and reactive compensations in industry, power transmission and distribution systems, utilities are widely used LC harmonic filers. The techniques are not that much suitable for commercial buildings and data centers, where the loads are mostly nonlinear with very high power factor close to unity. So it is not practical to use capacitors since there is no inductive power. LC harmonic filters are prone to easy overloading. They can create multiple resonant points which can interact with dynamic systems operation.
6. Six-phase transmission systems were initiated due to the rising cost of right of way for transmission corridors, environmental issues, and various stringent licensing laws. Six phase transmission lines can provide the same power capacity with a lower phase-to-phase voltage and smaller, more compact towers compared to a standard double-circuit three-phase line. The geometry of the six-phase compact towers may also aid in the reduction of magnetic fields as well. The disadvantage of the six phase system is that there is no inherent mitigation of harmonics, so additional action identical to three phase system need to be taken in order to mitigate harmonics.
The use of power handling systems is known in the prior art. More specifically, power handling systems previously devised and utilized for the purpose of generating, transmitting, and distributing electrical power are known to consist basically of familiar, expected, and obvious structural configurations, notwithstanding the myriad of designs encompassed by the crowded prior art which has been developed for the fulfillment of countless objectives and requirements.
While these devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not describe a five phase power distribution system with increased energy efficient and harmonic reduction.
In this respect, the five phase power distribution system according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides a system primarily developed for the purpose of increasing energy efficiency and reducing harmonics.
Therefore, it can be appreciated that there exists a continuing need for a new and improved five phase power distribution system. In this regard, the present invention substantially fulfills this need.